The class of mental state verbs (has thought to pose special problems for the young language learner. The precise source of these difficulties (mapping problems, conceptual limitations, etc.) Has been a mater of controversy. This research project starts out with the assumption that language acquisition often involves a mapping from an antecedently available concept onto a natural language label. It is hypothesized that this mapping may be particularly taxing for mental state verbs, the referents of which are abstract and hence unobservable. The goal of the project is to uncover circumstances or cues that should be helpful in the acquisition of such predicates. A series of experiments involving both child learners and adults is proposed to test these possibilities. This approach has several implications both for language acquisition and for the relationship between language and the ability to reason about mental states.